Well, that was fun while it lasted. This morning, the Sun published a story claiming that David Cameron is ordering his ministers to "get rid of all the green crap". But Downing Street has since said that "we do not recognise this at all". Call that a non-denial denial, as the New Statesman's George Eaton does, if you like – but Dave isn't ever going to 'fess up to talking about "green crap" in private, much less use the phrase in public.

Of course, what matters more than the wording is the policy: in that respect, there are plenty of signs that Cameron is moving away from the environmentalism he espoused early in his leadership. But the words matter still. It's striking that today's story comes from a "senior Tory source" who also says that "We used to say, 'Vote Blue, Go Green'. Now it's 'Vote Blue, Get Real'." Whether Cameron moderated his language or not, his colleagues clearly feel they don't need to – and that creates problems for the prime minister. He now has to back away from the story so that it doesn't clash too harshly with everything else he has said about the subject in the past.

This rhetorical wavering exacerbates one of the main problems with the Cameron premiership. Who is this man? What does he believe? It's never been entirely clear whether he was committed to the green agenda all those years ago, or whether it was simply a branding exercise. And that means that – now – it's not clear whether he's had a change of heart, or whether he thought it was crap all along, or whether he actually believes it all but is making concessions for electoral purposes. It's fine for a politician to change his mind, but they have to be clear about where their mind is. Otherwise, what are voters to think?

When I wrote on this theme last year, I said that Cameron needed to make a "big, open and comprehensive offer" to his party, much as he did to the Liberal Democrats after the last election …

This is why Mr Cameron should also make a 'big, open and comprehensive offer' to his own party. This doesn't mean a dramatic public speech, nor does it mean telling Tory MPs what they want they want to hear, rather than what they need to hear. But it does mean greater clarity about his brand of Conservatism, and an openness about where he agrees, disagrees and might compromise with other Conservatives. It also means a clearer sense of how any future Conservative majority administration would operate.

… and I still think that stands. Forget whether you agree or disagree with the green agenda, forget whether you're a moderniser or a traditionalist; an unclear Cameron helps no one's cause but Ed Miliband's. Until he conveys the force and direction of his convictions, no one will be truly happy. And "senior Tory sources" will go on hearing what they want to hear, or what they don't want to hear, whether the prime minister said it or not.